Lol at the PSA 10 1st ed Charizard, that card gets overpriced so often just because it's Charizard.
Well, the first thing that comes to mind is the Pikachu Illustrator card
https://archives.bulbagarden.net/me...uIllustrator.jpg/180px-PikachuIllustrator.jpg. There were only around six made, and it once sold for $20 000, though I have no idea what it might sell for now, probably still around there. It was a promotional card given away by CoroCoro to children who won a contest to design cards for the Japanese vending machine series. It's definitely the most coveted card out there for me, that's the first thing I would get if I became stupidly rich.
The next is probably prerelease Raichu, sold for something like $15K, I won't get into the details because people talk about it too much.
Then there are the Daisuku promos, given out in Japan only to people who participate in their tedious 'point system'. All of these cards are excedingly valuable, and printed in very few numbers. Perhaps one of the most famous of them is the Player's Umbreon:
https://cgi.ebay.ca/Umbreon-Star-70...U_CollectableTradingCards?hash=item3ef9ddc504
The other obvious cards that come to mind are trophy cards; the ones you can only get through winning tournaments, especially worlds, because there are so few of each printed (only three for each division).
https://cgi.ebay.ca/Pokemon-2002-Ba...emQQptZLH_DefaultDomain_0?hash=item563a6de57b Here's a good example, it's from the first battle roads ever held in Japan, less than ten ever printed. I don't know if it's actually worth 5K, but it's definitely one of the most expensive and unique out there. Even the cards released recently go for a few thousand a piece, with the No. 1 priced the highest every year.
If you're thinking of playable cards only, you are basically not looking at anything priced more than $50. It depends on how popular a card is for a certain region, but in my area Flygon lv X goes for $45, and it's probably the same way for Luxray in other areas. I don't think any playable card is worth more than that, and they are always accessible from Ebay or through investing in a booster box or two.